Disruption of the MFI framework by the incorporation of gallium

Abstract

The influence of isomorphous substitution of silicon by gallium in the MFI framework on lattice crystallinity and defect sites is investigated. The Ga-ZSM-5 zeolites are characterized by XRD, n-hexane adsorption, IR, TPD of ammonia, TG–DTA, MAS NMR, and chemical analysis. The incorporation of the large gallium atom is found to be disruptive. It leads to greater lattice distortion. However, the number of lattice defects decreases with growing gallium content. The sum of lattice defects and incorporated gallium atoms is nearly unchanged. It is suggested that gallium atoms and defect sites are located at similar lattice positions.